Many types of ordnance utilize two or more protruding surfaces to affect the fluid flow around the ordnance, thereby facilitating control of its trajectory toward a target. Exemplary types of such ordnance include missiles, rockets, guided projectiles, bombs, torpedoes and the like.
For example, missiles generally have an approximately cylindrical body, with at least two aerodynamic surfaces or fins that extend outwardly from the sides of the missile body to affect the aerodynamic characteristics of the missile in flight. The fins typically have an airfoil shape that is oriented edge-on or slightly inclined relative to the airflow when the missile is flying in a straight line. These fins may be, for example, static (fixed) or dynamic (selectively movable, i.e., controllable). Fixed fins generally are used to stabilize the missile during flight and do not move once fully deployed. Controllable fins (control fins) are used to control or steer the missile by selectively varying the attitude of the fins relative to the airflow under the direction of the missile's control system.
In many cases, the fins are stowed in a position adjacent the outside surface of or within the missile body during storage and mounting on a vehicle prior to use. In some cases, the missile is stored in a tube, canister or other protective casing, and the protective casing also may serve as a launch tube. The fins are stowed to reduce the effective diameter of the missile, permitting more missiles to be stored and/or transported in a limited space. It also reduces the likelihood of damage to the fins during storage and handling. Additionally, it allows for the maximum use of the internal space of the missile for electronic components and warheads.
The fins are extended from the stowed position shortly after deployment of the missile, either during mounting or launch of the missile. Various relatively complex deployment mechanisms have been developed to permit the fins to be stowed, deployed and locked into place. Control fins may further be moved (usually only rotated) by an actuator system once the control fins are deployed.
With regard to guided projectiles, in some cases, the fins are stowed by folding the fins like jack knifes or sling blades into the body of the projectile through longitudinal slots in the projectile's housing. Complicated retention features and housings are provided to retain the fins in the body of the projectile until the projectile has cleared the bore of the weapon system, e.g., a cannon, a gun, a howitzer, a mortar tube, or the like. For example, covers are employed to seal the longitudinal slots and retain the fins until needed in flight. In some cases, multiple mechanisms are used, for example, a cover deployment mechanism is provided to effectively discard the covers and a deployment mechanisms is provided to deploy the fins in flight.
The mechanisms presently used to retain, deploy and control (if applicable) the fins tend to be relatively heavy, complex and expensive to design, build and maintain. Moreover, some mechanisms occupy a relatively large volume within the missile, a significant disadvantage because of the limited space within the missile.